It's slightly below the recommended 700 watt threshold but my guess is that you should be fine. Both those cards combined have a TDP of 450 watts, and that's the maximum load that it probably wouldn't unless benchmarking. Verify that your existing power supply has another two 6 pin connectors of course.
I have an asus gtx 970 and i want sli it.
I want to know that will my corsair vs 650w psu enough for the sli??
You need 750w because as time passes PSU's capacitors are getting worse (aging).
Also corsair vs series are notorious for being unreliable i suggest something from the list that the guy on top said.(tier 1,2)